Expression of the Hox gene complex in the indirect development of a sea urchin
Expression of the Hox gene complex in the indirect development of a sea urchin
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DOI：
10.1073/pnas.95.22.13062
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发表时间：
1998-10-27
影响因子：
11.1
通讯作者：
Davidson, EH
中科院分区：
文献类型：
--
作者：
Arenas-Mena, C;Martinez, P;Davidson, EH
Hox复合体基因控制节肢动物和脊椎动物身体计划发展中的空间模式机制。Hox基因在这些群体中的胚胎发生期间全部表达，这些群体都是直接发育的生物体，因为胚胎发生立即导致形成各自成年体平面的主要元素。在最大限度地间接发展的各种无脊椎动物中，胚胎发生的过程只导致一个自由生活的，双边组织的摄食幼虫。最大间接发展的例子是海胆。海胆的5倍放射状对称的成年体平面是在胚胎发生完成后很久才产生的，通过在幼虫中留出的成虫组织内发生的单独过程。单一的Hox基因复合体的球海胆purpuratus包含10个基因，和这些基因中的8个的表达进行了测定，在胚胎和幼虫发育阶段，也在成人组织中的定量方法。这些基因中只有两个在胚胎发生本身的整个过程中被显著地使用，尽管所有这些基因在成虫体平面在成虫雏形中形成的阶段中都大量表达。它们在成体组织中也都以各种组合表达，因此，发育一种显微镜下的双侧等级的自由生活的生物体，幼虫，似乎不需要Hox基因簇的表达，而成体身体计划的发育需要。观察反映的机制，两侧后生动物可能已经出现在前寒武纪演化。
Hox complex genes control spatial patterning mechanisms in the development of arthropod and vertebrate body plans. Hox genes are all expressed during embryogenesis in these groups, which are all directly developing organisms in that embryogenesis leads at once to formation of major elements of the respective adult body plans. In the maximally indirect development of a large variety of invertebrates, the process of embryogenesis leads only to a free-living, bilaterally organized feeding larva. Maximal indirect development is exemplified in sea urchins. The 5-fold radially symmetric adult body plan of the sea urchin is generated long after embryogenesis is complete, by a separate process occurring within imaginal tissues set aside in the larva. The single Hox gene complex of Strongylocentrotus purpuratus contains 10 genes, and expression of eight of these genes was measured by quantitative methods during both embryonic and larval developmental stages and also in adult tissues. Only two of these genes are used significantly during the entire process of embryogenesis per se, although all are copiously expressed during the stages when the adult body plan is forming in the imaginal rudiment. They are also all expressed in various combinations in adult tissues, Thus, development of a microscopic, free-living organism of bilaterian grade, the larva, does not appear to require expression of the Hox gene cluster as such, whereas development of the adult body plan does. observations reflect on mechanisms by which bilaterian metazoans might have arisen in Precambrian evolution.